SPONGES, GRAPTOLITES, CORALS. 65 
Ischadites,] 
observed of one of the horizontal rays of a spicule extending beyond the distal 
angle of its summit-plate over that of the one immediately in front. Vertical rays 
of spicules subeylindrical, about 15 mm. in length. 
The above synonomy and Receptaculites ohioensis Hall and Whitfield, FR. sub- 
turbinatus Hall, and R. jonesi Billings, Dr. Hinde regards as embracing but a single 
species, Ischadites kenigii Murchison. Rf. ohioensis and R. subturbinatus are from the 
Niagara group of Ohio and Indiana ; the first differs in the comparatively large head- 
plates and in its strongly convex base, while the latter has much larger head plates 
on the sides than Ischadites iowensis. R. jonesi agrees with Ischadites cowensis in form 
but as it is from a later geological horizon, we prefer to retain the species, partic- 
ularly since we have no examples for comparison. Ischadites iowensis is constantly 
more or less strongly concave, never conical, and but rarely flattened on its under side. 
It attains a larger size and has comparatively smaller head-plates than L. kenigii. 
Since these features are constant in I. iowensis, we deem it sufficient ground to retain 
this species as distinct from that form. 
All the specimens of J. iowensis from Minnesota, seen by the writers, are de- 
pressed sub-globose, never sub-turbinate. J. fungosus Hall might be recognized as a 
good variety, were it not that both forms have been found lying with the umbilicated 
side downwards within a foot of each other, in the side of a cliff at Decorah, Lowa. 
Formation and locality —Galena formation of Iowa, Wisconsin, and Minnesota, In Minnesota, this 
species is usually obtained from the lower portion of the Galena; some localities are six and twelve miles 
south of Cannon Falls in Goodhue county, and Wasioja, Dodge county. Mr. F. W. Sardeson informs the 
writers that he obtained this species in the Hudson River or Cincinnati group, near Spring Valley, 
Minnesota. 
Mus. Reg. Nos. 5839, 6760, 7250. 
SYNOPSIS OF AMERICAN SPECIES OF ISCHADITES. 
I. CYATHIFORMIS Hall. 
1847. —— cyathiformis HALL. Paleontology of New York, vol. i, p. 72, pl. 25, fig. 6a-6e. 
Closely related to J. iowensis. 
Formation and locality.—Trenton limestone ; Carlisle, Pennsylvania. 
I. CIRCULARIS Hmmons. 
1885. Receptaculites circularis Emmons. American Geology, pt. ii, p. 280, fig. 82. 
1891. Receptaculites circularis JAMES. Jour. Cincinnati Soc. Nat. Hist., vol. xiv, p. 63. 
This species may be identical with I. Jowensis, but the spicular head plates seem to be larger. 
Formation and locality. Loraine shales ; New York. 
I. JONESI Billings. 
1865. Receptaculites jonesi BILLINGS. Paleozoic Fossils, vol. i, p. 389, fig. 365. 
1865. Receptaculites jonesi BILLINGS. Canadian Naturalist and Geologist, sec. ser. vol. ii, p. 191, fig. 12. 
1884, Ischadites kenigii (partim) HINDE. Quart. Jour. Geol. Soc. London, vol. xl, p. 836, 
See remarks on this species under J. owensis. 
Formation and locality.—_Lower Helderberg group ; Cape Gaspé, 
